"This is where something like the Seagate Portable External Hard drive
comes in. It’s a good compromise between the two, being portable yet
also offering a decent capacity, with 160GB the largest size currently
available. The drive inside spins at 5,400rpm, and has 8MB of cache, as
you’d expect of a standard drive. There is a version available that
spins at a faster 7,200rpm but that’s only available at a capacity of
100GB."